Retinal oxygen delivery and extraction in ophthalmologically healthy subjects with different blood pressure status

Abstract

Purpose: To compare retinal oxygen delivery (DO2) and extraction (VO2) in ophthalmologically healthy subjects with different blood pressure (BP) status. Methods: In this case-control study, we prospectively included 93 eyes of 93 subjects (age 50-65) from a large-scale population-based Dutch cohort (n=167,000) and allocated them to four groups (low BP, normal BP [controls], treated arterial hypertension [AHT], untreated AHT). We estimated vascular calibers from fundus images and fractal dimension (FD) from optical coherence tomography angiography scans. We combined calibers, FD, BP, and intraocular pressure measurements in a proxy of total retinal blood flow (RBF), using a validated Poiseuille-based model. We measured arterial and venous oxygen saturations (SaO2, SvO2) with a two-wavelength scanning laser ophthalmoscope. We calculated DO2 and VO2 from RBF, SaO2, and SvO2. We compared DO2 and VO2 between groups and investigated the DO2-VO2 association. Results: DO2 and VO2 were different between groups (P=0.009, P=0.036, respectively). In post hoc analysis, the low BP group had lower DO2 than the untreated AHT group (P=4.9⋅10-4), while both the low BP group and the treated AHT group had lower VO2 than the untreated AHT group (P=0.021, P=0.034, respectively). There was a significant DO2-VO2 correlation (R[obs]=0.65, b[obs]=0.51, P=2.4⋅10-12). After correcting for shared measurement error, the slope was no longer significant (b[cor]=0.19, P=0.29), while the correlation coefficient could not be calculated. Conclusions: DO2 and VO2 were altered in ophthalmologically healthy subjects with different BP status. Future studies could elucidate whether these changes can explain the increased risk of several ophthalmic pathologies in those subjects.